Cousin is Tausoga, so the literal translation is "Ou te alofa ia te oe, Tausoga" like in, "I love you, Brother" - "Ou te alofa ia te oe, Uso". Rather than using Tausoga, Samoans tend to use the word "Uso" to relate to anyone who is related to them, and even friends.
Ou te alofa ia te oe, la'u Uo.
Lo'u alofa
Tofa
Im not too sure how you say lover but love in Samoan is 'Alofa' Hope that kind of helps!!
O e gaualofa?
You can always tell your cousin you love them. But it is not commen to love your cousin like a girlfriend or boyfriend.
You can say "miss you" in Samoan as "ua ou misia oe."
Alofa i tagata uma
i koam sei me loave
Alofa i lou tina.
Literally, alofa fa'asaina
Alofa le fa'atuaoi'ina
Oute Alofa Ia Oe