Sidney is perfectly fine for a boy.
Sidney James sounds great. I also like
Sidney Alexander.
Morgan,
Sidney,
Mackenzie, and
Madison is a decent sibset, but I think that there are too many names beginning with M, which could end up confusing people. I really like the name
Mackenzie for a boy, but I would avoid using
Madison since it's so common for girls. I prefer
Addison. I have actually only met one
Madison personally, and the person was male. He was probably in his 40s though. I've also met a male
Morgan (he is about 20 years old now).
I don't care for the sound of
Eartha, but
Ocean is a nice name for a girl.
Ocean combos:
Ocean ClaireOcean Clarice /
ClarisseOcean Victoria - Does it sound too much like a cruise ship though?
Ocean DanaeOcean LorraineOcean Fay /
FayeOcean MariahOcean MariahOcean Marie - Too boring?
Ocean RebeccaOcean Veronica