Hmm, LeeAnne is already composed of 2 names, don't you think another 2 names would be too much? Just my opinion... How about
LeeAnne
Savannah -
1.
Lee = meadow, pairs up with
Savannah ;)
2. Or
Lee as a form of
Leah - gazelle +
Anne - grace -> LeeAnne = graceful gazelle - sounds good with
Savannah :)
3. Or
Lee as a form of
Leah, which could mean "mistress" -> LeeAnne
Savannah - graceful mistress of the savannah and
Ryan Gratian Leslie -
Ryan - little king,
Gratian - graceful,
Leslie - meadow land ->
Ryan Gratian Leslie - graceful king of the meadow. I do hope your BIL's last name is not
Leslie :)...
Hope that stirs some ideas :o)