I love both my nephews, Max and Teagan, who were just here for a visit from Colorado, with their mom, Em. (I love Em too, btw. I treasured every moment, most of them interrupted by many things - namely children, we had together. I felt a funny, empty, sad feeling when she left after a lovely but way too short visit.)
Max is 4 yrs old and quite a charming and talented fellow. Teagan is only one yr old. Other ages have their appeal, but for sheer cuteness, you can't beat a one year old. You can try, but you just can't.
A testament to the warmth and cooperation between the four-yr-old cousins is evidenced by Max playing with Jasper's special sparkly sword. No one ever gets to play with that sword except Jasper, but Jasper willingly let Max have a turn. No one even asked him too (I wouldn't usually make such an extreme request of him...)