
I've been replaying OoT and I plan to do MM next. XD
But I agree, the fact that it's Miku who goes after the eggs and not one of the others pretty much states that he has a personal interest in Lulu if not in the eggs themselves. I always figured that the eggs had to be his as well though- it doesn't seem logical that the female Zora would have eggs on their own without any input from the male, and that if a male was needed, Lulu would be with anyone but Miku.
That scene with Lulu and Miku though, them holding hands is the biggest indication in itself; the song of Healing brings peace to the troubled souls regarding the things that mattered most. With Darmani we see all the Gorons cheering for him; he takes care and protects them. With Miku it's Lulu in the forefront and then the rest of the band in the back. If that makes any sense.