I recall that Prince William has been an AV fan since his youth, so it's not surprising that his children have been aware that their father watching the team's matches for years
Yeah, he's said that while George is definitely a Villa supporter, Charlotte and Louis claim to be, but he's not holding them to that, wanting them to decide on their own which team they support as they get older and more into the game, which is fair.
As for William's friends, I don't know which teams they support, but as a huge football fan myself, I know this:
1. If my friend offered me tickets to a Champions League match — any Champions League match — I would go with no hesitation.
2. You don't have to be a fan of a team to go to a match, enjoy it, and get into it. I'm not a Barcelona fan at all, but when my friend and I went to a match at the Camp Nou while we were on vacation, I found myself swept up in the crowd's excitement and cheering every goal, even though I was bitter that my own team's best player had recently signed with Barcelona.
3. If you don't already have an allegiance to a team, you can become a fan of a team that a friend or family member is passionate about. My brother is a huge Arsenal supporter and I started out watching matches with him purely as a way to spend more time with him and understand something he loved so much. Twenty years later, I think I'm an even more fanatical Arsenal supporter than he is. I can definitely relate if that's how William's friends have come to support Villa. Indeed, that's the way William himself
became a supporter:
“Aston Villa’s always had a great history. I have got friends of mine who support Aston Villa and one of the first FA Cup games I went to was Bolton vs Aston Villa back in 2000. Sadly, Villa went on to lose to Chelsea.
“It was fantastic, I sat with all the fans with my red beanie on, and I was sat with all the Brummie fans and had a great time. It was the atmosphere, the camaraderie and I really felt that there was something I could connect with.”
In any case, I loved seeing William and George's reactions to the Villa match. Even though they fell short, Villa's comeback was so exciting. Personally, I'm relieved, though, because had they progressed, Arsenal and Villa would have played in the semi-finals, and I hate playing other Premier League teams in the Champions League. Crisis averted. Sorry, William and George!