William and Lillian-too similar? What to do?!

Isla

We have a 5 yo girl named Lillian and we have ALWAYS loved the boy name William first before Lillian was born. We just had a son and named him William but now I’m having second thoughts on if it’s too similar to Lillian. My husband just loves the name and thinks it’s fine. I am super concerned that I want my son and daughter to feel like individuals. But now it feels impossible to change his name even if we wanted to. My daughter even commented how the names sound similar.

We use nicknames for Lillian - Lil, Lilly and Lilla. We could do Liam or Will… I even thought of Leo. (Is Leo too much of a stretch bc I love it and almost don’t care!) But they are all so similar with L short names!!! Or is it cute they kind of go together? I’m worried people will call them Lilly and Willy - don’t like Willy.

The runner up name I loved is Everett but is it crazy to change names now a month after he’s been born. A name is so sentimental. His middle name is James bc of late father in law. I just want me son to have a special name. I wish he could choose now :(

What do I do?!