Nobody can stop you from having a character name that doesn't suit your race's lore as long as you have a reason behind it. Actually, even if you had no reason at all nobody could stop you.
I'm not sure I understand why you want a Sun Seeker how is 'attuned' to the moon. But I guess what you mean is that you like the Sun Keepers' aesthetical appareance but you prefer Moon Keepers' name, correct?
If that's the case, you can handwave it by making this character a Sun Keeper adopted by a Moon Keeper family. It's probably best to make them city-dwellers, too, since the city-states is where the cultures meet and merge, so naming conventions can be bent more reasonably. A tribal setting could work too, though.
Personally, I'd just go full Sun Keeper and adapt the name. Being a Sun Keeper with an attunement to the moon sounds incredibly odd and will send the wrong message to other roleplayers. But, as stated, being raised in a nocturnal family can explain it quite well, I think.
I'm not sure I understand why you want a Sun Seeker how is 'attuned' to the moon. But I guess what you mean is that you like the Sun Keepers' aesthetical appareance but you prefer Moon Keepers' name, correct?
If that's the case, you can handwave it by making this character a Sun Keeper adopted by a Moon Keeper family. It's probably best to make them city-dwellers, too, since the city-states is where the cultures meet and merge, so naming conventions can be bent more reasonably. A tribal setting could work too, though.
Personally, I'd just go full Sun Keeper and adapt the name. Being a Sun Keeper with an attunement to the moon sounds incredibly odd and will send the wrong message to other roleplayers. But, as stated, being raised in a nocturnal family can explain it quite well, I think.