#3 Roman Reigns def. Rey Mysterio (WWE Money in the Bank 2021)
If Roman Reigns faces The Rock at WrestleMania 37, his Universal Championship reign will likely continue into the summer months because there is no way he is losing to his part-timer cousin. WWE would need to line up a couple of challengers for him to face before ultimately losing the belt.
One of them would be Rey Mysterio, who is among the top babyfaces on SmackDown. There is no telling when his storyline with Seth Rollins and Murphy will end, so, to be safe, he would come into the world title picture after WrestleMania.
Mysterio is a timeless performer and would give Reigns another excellent title defense. He and Dominik could even move to the tag team division to face The Usos after this match.
#2 Roman Reigns def. Kevin Owens (WWE Backlash and Extreme Rules 2021)
Having been mentioned earlier, Kevin Owens should have a full-blown Universal Championship program against Roman Reigns. He has barely scratched the surface as a babyface, a role he can do so much more in. KO would have initially supported Daniel Bryan in his Universal Title chase, but he is also a compelling contender to Roman Reigns' crown.
The two of them have incredible chemistry, as proven by their feud four years ago. Reigns and Owens can have multiple pay-per-view title matches, culminating in a brutal Extreme Rules Match at the namesake pay-per-view, not too dissimilar to their No DQ brawl at Royal Rumble 2017.
After another successful program alongside a top babyface on SmackDown, Roman Reigns would finally meet his match. Somebody who his cousins know very well.