Would you consider [name_f]Mary[/name_f] [name_f]Lucille[/name_f]? It is just so beautiful!
My almost-30-year-old stepdaughter is [name_f]Lucille[/name_f] [name_f]Claire[/name_f] & has always gone by [name_f]Lucy[/name_f]. She has complained that her name is popular…for small dogs. I don’t know if this is a concern for you, but as she’s mentioned it repeatedly, I thought I should at least mention it.
[name_m]Anders[/name_m] in particular strikes me as Scandinavian…would [name_f]Lucia[/name_f] be an option? There’s a St. [name_f]Lucia[/name_f] whose day is celebrated in early [name_u]December[/name_u]. Also related to the [name_f]Lucy[/name_f] family is [name_f]Lucinda[/name_f]. Here’s a link to other girls’ names that start w/[name_m]Luc[/name_m]: https://www.babynamespedia.com/names/girl/luc-start
[name_f]Mary[/name_f] is just not my cup of tea, & while hardly used today, seems plain when compared w/your boys’ names. Would another form of [name_f]Mary[/name_f] work? Maybe…
[name_u]Marian[/name_u]
[name_f]Marianne[/name_f]
[name_f]Miriam[/name_f]/[name_f]Mariam[/name_f]
[name_f]Malia[/name_f]
[name_f]Miren[/name_f]
[name_f]Maura[/name_f]
[name_f]Ruth[/name_f] is definitely a strong name & [name_f]Ruthie[/name_f] is very cute!
[name_f]Ruth[/name_f] [name_f]Lucille[/name_f]!
My favorite from your list is [name_f]Ruth[/name_f] [name_f]Lucille[/name_f].
I know of a [name_f]Ruth[/name_f] [name_u]Evelyn[/name_u] and a [name_f]Mary[/name_f] [name_f]Claire[/name_f] in real life (old ppl). 
I am NOT an “I love [name_f]Lucy[/name_f]” fan… a silly loud-mouth really.
My choice would be [name_f]Merryn[/name_f] [name_f]Claire[/name_f], but I’m not sure if it matches with your boys.
I know a young girl that is named [name_f]Mary[/name_f] [name_f]Grace[/name_f] and I think it’s lovely. She uses both names.
[name_u]Love[/name_u] [name_f]Ruth[/name_f] nn [name_f]Ruthie[/name_f]
While I’m a [name_f]Lucy[/name_f] (although spelled differently) and I do love the name, I like [name_f]Ruth[/name_f]/[name_f]Ruthie[/name_f] better with your sibset and [name_f]Ruth[/name_f] [name_f]Lucille[/name_f] is a great combo. Interesting tidbit-- if people mistake my name, they usually think I’m [name_u]Lisa[/name_u] or [name_f]Ruthie[/name_f].
[name_u]Love[/name_u] love love [name_f]Ruth[/name_f] nn [name_f]Ruthie[/name_f] with your boys! Definitely my favorite. That or [name_f]Lucille[/name_f] nn [name_f]Lucy[/name_f]
7th heaven fan?
Yes, all 7th [name_f]Heaven[/name_f] names!
I prefer [name_f]Lucy[/name_f] from your list. It’s the most lively and charismatic - yet it’s also a classic. I don’t find it trendy necessarily, but it isn’t uncommon. It’s sort of like [name_f]Molly[/name_f] or [name_f]Annie[/name_f]. [name_f]Ruthie[/name_f] would be my second choice, even though I find [name_f]Ruth[/name_f] to be quite stern and solemn. [name_f]Mary[/name_f] is refreshing to hear these days, but it’s never going to be interesting because of past centuries of over-use. Pairing it with something unexpected to make a double first could make it stand out, like [name_f]Mary[/name_f] [name_f]Opal[/name_f] or [name_f]Mary[/name_f] Lieve.
Definitely [name_f]Mary[/name_f].
I like [name_f]Mary[/name_f] [name_f]Claire[/name_f], a lot.
Would you consider…[name_f]Mary[/name_f] [name_f]Alice[/name_f]…[name_f]Mary[/name_f] [name_f]Gwendolen[/name_f] ([name_f]Mary[/name_f] [name_f]Gwen[/name_f]) ???
OR…[name_m]How[/name_m] about [name_f]Margaret[/name_f] [name_f]Claire[/name_f] ([name_f]Meg[/name_f], [name_f]Margot[/name_f], [name_f]Maggie[/name_f])???
[name_m]Ander[/name_m]$ Br@m, Gide0n and M@rgot
[name_f]Ruth[/name_f] [name_f]Lucille[/name_f] – perfect.
[name_f]Ruth[/name_f] [name_f]Lucille[/name_f]!
Overall, I’m inclined to go for [name_f]Lucy[/name_f] here! I think it suits your sibset perfectly, and it’s just such a sweet name. There’s a lightness to it I find charming; and it complements your sons’ names well (which are lovely btw!). Might be a bit of a stretch, but if you’re really fond of [name_f]Ruth[/name_f] [name_f]Lucille[/name_f], you could even have the nickname there be [name_f]Lucy[/name_f]? I know plenty of people who derive a nickname from their middle name!
As @babymagic suggested though, I think [name_f]Mary[/name_f] [name_f]Opal[/name_f] is a beautiful combination, and really creates a nice refreshing element to a name that used to be so widespread! So if you feel maybe [name_f]Mary[/name_f] is better, I think that’d be a nice alternative?
[name_f]Ruth[/name_f] and [name_f]Lucy[/name_f] are wonderful names. I slightly prefer [name_f]Ruth[/name_f] as it is an uncommon name and of course, [name_f]Ruthie[/name_f] as a nickname is incredibly sweet and quaint.
[name_f]Mary[/name_f] or [name_f]Ruth[/name_f]! [name_f]Lucy[/name_f] has been used too much.