A family set should be coherent, not coordinated
Siblings are individuals, so their names do not need a shared first letter or theme. What usually matters is a subtler balance. A very formal historical name beside an invented nickname can feel uneven to some families; to others, that contrast records two different stories and is exactly right.
Say the pair as you would use it at home. Then reverse the order. If both names collapse into the same nickname or differ by only one sound, daily use may be less clear than it looks on paper.
Keep culture and family history in the decision
A ranking cannot tell you whether a grandparent's name, a bilingual spelling or a religious tradition belongs in your family. Use the results to widen the shortlist, then verify pronunciation and meaning in the language that matters. Our source-based naming tradition guides are a better next step for that work.
Finish the full name
Once a first name survives the sibling test, put it beside the surname and likely middle names. The middle name generator checks that longer line, while the unisex baby names guide offers choices recorded for both boys and girls.