Does anyone think that [name_f]Lyla[/name_f] is too close to [name_m]Elijah[/name_m] to use it as a sib set?
Nope, I think it’s fine. They both share the “lie” but they’re not too close at all.
I think It’s fine
I personally wouldn’t use them as siblings but on paper and in regular conversation it works fine. It can get confusing trying to yell for them 
I also think it sets a precedent for the following children to either sound off/accidental OR overly matchy like [name_m]Elijah[/name_m], [name_f]Lyla[/name_f], and [name_u]Rylee[/name_u].
I think that [name_m]Elijah[/name_m] and [name_f]Lyla[/name_f] are too close for comfort. Some other suggestions are:
[name_f]Cyra[/name_f] ([name_m]Keer[/name_m]-ah)
[name_f]Lilia[/name_f]
[name_f]Lydia[/name_f]
[name_u]Evelyn[/name_u]
[name_f]Laila[/name_f]
[name_f]Mila[/name_f]
Growing up, my brother’s name was [name_m]Thomas[/name_m] and our family pet’s name was [name_f]Comet[/name_f]. They have about equal similarity to each other as [name_f]Lyla[/name_f] and [name_m]Elijah[/name_m]. I can’t tell you how many times my mother would get tongue-tied and end up saying Tomet. That gets annoying for everyone. I’d suggest going with [name_f]Leila[/name_f], [name_f]Lydia[/name_f], [name_f]Lana[/name_f], [name_f]Lena[/name_f], [name_f]Leona[/name_f], [name_f]Lucia[/name_f], [name_f]Luna[/name_f], [name_f]Liesl[/name_f]…
It’s too close for me, but I think it’s fine. I don’t think the average person would notice really. Families have similar sounding names all the time.