Oftentimes in sports, family and heritage mean a lot in determining a player's talent and chances of making the big leagues. There is a reason why a lot of pro players in any sport have very athletic parents or parents that played professional sports as well. Of course, this isn’t always the case, but it seems to be fairly widespread. It’s not surprising to see professional players that have a father or mother that was involved in the sport as well.

And if parental lineage is so important in breeding star athletes, why are there so few siblings in pro sports? That simply breaks down to the fact that though siblings may both play pro sports, there is likely one that is more talented and that’s just how the world works, as some people are just blessed with more talent than others.

We all know the siblings in sports like the Williams sisters in tennis, the Manning brothers in the NFL and more. But there are many more athlete siblings out there in the world that no one really knows about, and that will be the focus of this list. This list will look at some of the most obscure athlete siblings of all time. Some played in the same sports as their famous siblings, and some played in different ones.

So read on and enjoy the Top 15 Athletes Who You Didn’t Know Had a Sibling in Pro Sports.

15 15. Jose Canseco

Jose Canseco is one of the most polarizing figures in MLB history and was at the forefront of the conversation during the steroid era of baseball. What most people don’t know, however, is that Canseco has an identical twin brother who also played in the MLB. Ozzie Canseco only appeared in 24 games in three years in the MLB, but is still involved with baseball up to this day. Ozzie has made numerous public appearances in place of Jose for events such as baseball card shows and book signings.

14 14. Horace Grant

Horace Grant is a former NBA player who has played on four championship teams and is perhaps best known for his trademark protective wraparound eyeglasses and as part of Michael Jordan’s supporting cast in Chicago. Though most people know who Horace is, few people know he also has a twin brother who also played in the NBA. Harvey Grant was a first round pick that had a fairly decent 10+ year NBA career with multiple teams and averaged about 10 PPG for his career.

13 13. Reggie Miller

Reggie Miller is one of the greatest shooters and clutch performers in NBA history. If you are a fan of the NBA, you likely know who he is. What you might not know, however, is the Reggie has not one, but two siblings who were involved in pro sports. His brother, Darrell, is a former MLB player who appeared in more than 200 career games. And his sister Cheryl is a member of the Pro Basketball Hall of Fame and was one of the most dominant female college players of all time.

12 12. Jason Giambi

Jason Giambi was a big time slugger in the MLB and was a five time all star who won the 2000 AL MVP. He had one of the better careers in MLB history, but his later admission to using PED's has led some to question a lot of his accomplishments. What a lot of people don't know about Jason is that he has a younger brother that also played in the MLB. Jeremy Giambi played in the MLB for six years and enjoyed moderate success, but wasn't able to put up the numbers that his brother did.

11 11. Michael Schumacher

Michael Schumacher is without a doubt one of the most talented and successful racers in F1 and was a seven-time champion. He is often regarded as one of the best drivers of all time and holds numerous records. What most people don’t know about Michael is that he also has a brother who raced in F1. His brother, Ralf, also was a successful racer who has won his fair share of races, despite not being as successful as Michael. These brothers also share the honor of being the only siblings to have won races in F1.

10 10. Champ Bailey

Champ Bailey is often regarded as one of the best cornerbacks in NFL history. He is a multiple Pro Bowl and All Pro award winner and a member of the All Decade team of the 2000s. What many people don’t know is that he is the brother of another former NFL player. Boss Bailey, best known for his time with the Detroit Lions, is the younger brother of Champ Bailey. Boss played in the NFL for five years and was named an NFL All Rookie in 2003 with 88 tackles, 1.5 sacks and 1 interception.

9 9. Mark McGwire

Mark McGwire is one of the biggest bats in the history of the MLB and is a multiple time all-star who won a World Series championship. He has admitted to using PEDs throughout his career, which has led some to put an asterisk next to his stats. What surprises most people about McGwire is that he has a brother who was in the NFL. In fact his brother, Dan McGwire, was first round pick as a QB, but ended up fizzling out of the league in a few years after him being drafted.

8 8. Michael Vick

Michael Vick has been one of the more polarizing figures in the NFL for years and is one of the best mobile QBs of all time. He has also done terrible things off the field, but there is no denying his skill on the field. This is very similar to his brother, Marcus Vick. Marcus had a lot of talent on the field, but many off the field issues throughout college and that held his NFL career from ever really take off.

7 7. Hank Aaron

Hank Aaron is one of the most influential stars in MLB history and was the all-time home run leader in history for 33 years and is a member of the Hall of Fame. With accolades like that, it makes sense that he would overshadow his brother. His brother is Tommie Aaron, who was not able to live up to his brother's high standards. The two were also teammates and the first siblings to appear in a League Championship Series as teammates.

6 6. Cal Ripken

Cal Ripken will go down in history as one of the most productive and tough players in MLB history. He was the inspiration for bigger and more powerful shortstops that we saw in the 2000s and onward. Cal’s brother, Billy Ripken, didn’t have nearly the career that Cal did, but still had a 10+ year stint in the majors. Billy and Cal were actually teammates and played second base and shortstop respectively, being only the fourth siblings of all time to do that.

5 5. Jackie Robinson

Jackie Robinson is one of the most important players in the history of baseball, as he was the first African-American player in the major leagues. He had a great 10 year career in the majors and opened up the door for the multicultural MLB that we have today. His brother, Mack Robinson, was also an extremely successful and talented athlete. Mack is an Olympic runner who won the silver medal at the 1936 Berlin Olympics in the 200m race and set various junior college records.

4 4. Steph Curry

Yes, the reigning NBA MVP and best shooter in the league has a brother who plays in the pros. Despite not having the same NBA success, Seth Curry is also a pro basketball player. In fact, Seth played at a bigger school than Steph and put up some respectable numbers in college. He went undrafted but has been on various NBA teams and currently plays in the NBA Development League. Their father, Dell Curry, was also a great NBA player in the 80s and 90s.

3 3. Wayne Gretzky

Wayne Gretzky is without a doubt the best player in NHL history and one of the most dominant athletes in any sport. He still holds numerous NHL records, some of which are likely to never be broken. Wayne actually had not one, but two brothers who were in the NHL. Brent was a member of the Tampa Bay Lightning for a few games, but eventually went on to play pro hockey for various other leagues after fizzling out of the NHL. And Keith, who was drafted by the Buffalo Sabres and attended training camps and pre-season games, but never played in an NHL game.

2 2. Rob Gronkowski

Gronkowski burst onto the scene in the NFL a few years ago and is now regarded as one of the best tight ends in the NFL. He is a touchdown scoring machine and, if he keeps up his current pace, he might become considered the best tight end of all time. However, Rob isn’t the only tight end in the Gronkowski family. His brother, Dan, was also a tight end in the NFL from 2009-2011 with multiple teams, but never was able to stick on a roster. He had another brother make it to the NFL as well, Chris, who was a fullback who was in the league for three years.

1 1. Blake Griffin

Blake Griffin is a former first overall pick and is a multiple time all-star and All NBA award winner. He is one of the most exciting high flyers in the league and has recently added new elements to his game to make him even more dangerous. One thing that almost no one knows about Blake is that his brother, Taylor, is a former second round pick. Taylor Griffin was drafted by the Phoenix Suns and is now currently playing in the NBA Development League after bouncing around a few other teams.