I've been fond of
Jerome since I was very young, partly because of the sound and feel of the name, but also influenced by one of my favorite story books:
http://www.ebay.com.au/itm/JEROME-Frog-Witch-story-1967-Ressner-PARENTS-MAGAZINE-PRESS-/201285684534
Never have understood why it isn't more popular.
Marcel isn't a personal favorite on paper, but I used to know a very sweet boy by the name so I have good associations; I think he'd be about college age now.
I also quite like
Gerard, though I do prefer the first syllable stressed, personally. Of the names you mention, I think
Jerome and
Marcel are most interesting together as siblings, but
Gerard and
Marcel work nicely too.