Gosh gorgeous sibling set 
Favourite to least favourite…
Clara ~ I love this name she’s beautiful really princessey and bright with European flair however this feedback is only in relation to KLAARA pronunciation. However Clair-uh isn’t my favourite pronunciation.
Sylvie/Sylvia ~ Sylvie is beautiful, ethereal, majestic and peaceful with the lovely meaning ‘from the forest’ I love the overall feel of Sylvie! Sylvia is also gorgeous feels more ‘vintage’ less carefree maybe more formal feeling but also stunning. I think Sylvie is a better fit.
Faye ~ I love the fairytale fairy feel of Faye! Faye is a bright, whimsical choice and sounds gorgeous with Martha + Robin. Love Faye!
Abigail ~ I really like Abigail she used to not be a favourite of mine but I think she’s becoming a slow burning new crush honestly I can completely see why she’s loved by many! Abigail is strong, biblical, elegant, has the wonderful meaning ‘father’s joy’ and the sweet nickname Abby.
Lydia ~ another pretty biblical name with a melodic L sounds she’s elegant, strong and has a sing song sound. She’s lovely.
Hattie ~ she’s adorable, spunky, with a sweet vintage flair very happy and has a fun feel. However does feel a bit juvenile paired with Martha but works well with Robin.
Julia ~ a very timeless name she’s strong, graceful and has a summery vibe. I think Julia is a lovely name but I do feel that Juliet would be a better fit.
Joyce ~ this name rates the same as Julia in my eyes I like her just as much Julia however I think Joyce has the right vintage flair with Martha + Robin sounds aesthetically gorgeous. Such a call the midwife aesthetic so lush.
Lena ~ I do like Lena very elegant with a European flair but doesn’t fit that well with Martha + Robin in my opinion just feels very different.
Mabel ~ Mabel is a sweet name with a pretty meaning however does feel very trendy rather than the sweet unexpected flair of Martha + Robin. Also I’m not a fan of Mabel + Martha with the repeated ‘ma’ starts.
Hope this helps