My favorites from your list are
Max, Felix, and Jasper
Max, Felix, and Iris
I also love the suggestion of Julian for a boy. And I have the same problem as you with Annie. Love the nickname, not so much the longer forms. Have you considered names that end with anne? Like Julianne, Lilianne, Marianne?
So this is how our list is looking at the moment... it seems to be growing instead of shrinking, number three is definitely the hardest to name so far!! Please be as honest as you can about them, we are more concerned with finding a fantastic name that we love than one that is a 'perfect fit' with its siblings (though it would be great if it was as well)!!
Anthea (nn Annie)
Hazel (thank you for the suggestion sunshine.10!!)
Thank you again for replies! Why is naming number three so hard, we can't seem to narrow it down at all! Any more opinions/ideas?
Well naming #3 is hard because you already used your favorite two names for boys and now you really want to find a third name that you love just as much. Problem of course is that you've had some time to fall more in love with Maximillian and Felix (and not just the names) and it's going to be hard to find a name that remotely holds up to those standards. lol. But you'll figure it out - I promise. ;)
Harold - Oh Harold is handsome. I know it was a front runner when you opened this thread but since you didn't state so in your last round up I assume it's just not quite perfect. How about Harvey?
Grover - I see it's appeal, but I can't get over the Sesame Street Grover and I also keep thinking about dogs (maybe too much Rover).
Jude - Ordinarily I like this name I just don't love it with Max and Felix. Jude, is soft and handsome and sensitive, it feels like it's missing a bit of the backbone that makes Max strong and Felix spunky.
Jasper - Oh this makes me swoon. Jasper and Felix are two of my all time favorites (the only reason Jasper isn't on my top ten is that is has no charm in German or Spanish). Maximillian, Felix and Jasper would be my perfect combo from your list.
Samuel - It's a gorgeous name I just don't love it for you. To me it lacks spunk.
William - I love it and I think nn Liam would be pretty awesome with Max and Felix.
Walter - Even though I know a Walter who is my age this always feels like an old man name to me. It feels like it's from a different era than Maximillian and Felix.
Edward - I like the funky w in the middle of the name to go with the crazy x's.
Asher - Soft and gentle see Jude.
Joel - Handsome but you have better on your list.
Florence - nms.
Iris - oh this is an adorable match for your boys. Short, spunky, and with ageless history.
Rose - I love how beautiful and soft this name is. While I don't like those qualities in boys choices i do love it for girls.
Anthea (nn Annie) - this is cute I'd go with nn Thea instead, keeps the feel and integrity of the name better than Anthea. To me at least.
Beatrice - This is beautiful and soft. One of my favorite choices for your sib-set on your current list. (I assume you'd avoid Trixie as a nn?)
Stella - I don't love it but it's nice.
Hazel (thank you for the suggestion sunshine.10!!) - great suggestion.
Heidi - I don't understand why everyone loves this. It's so old lady on the mountain to me. But I did grow up a few hours away from where "Heidi" originated so maybe that's my issue with it. It's like the little girl version of Gertrude to me.