Formal:
* Cariad parhaol, brawd. (Love lasting, brother) - This is the most literal translation, but it might sound a bit stiff.
* Cariad parhaol i ti, brawd. (Love lasting to you, brother) - This is a more personal and affectionate way to say it.
Informal:
* Caru di bob amser, brawd. (Love you always, brother) - This is the most common and natural way to say it.
* Dwi'n dy garu di bob amser, brawd. (I love you always, brother) - This is a more emphatic way to say it.
* Caru di, brawd. (Love you, brother) - This is a simple and affectionate way to say it.
More creative:
* Bydd cariad yn parhau rhwng ni, brawd. (Love will remain between us, brother) - This is a more poetic way to say it.
* Rwy'n dy garu'n fawr iawn, brawd. (I love you very much, brother) - This is a more heartfelt way to say it.
Ultimately, the best way to say "love always, brother" in Welsh is to choose a phrase that feels right to you.