Ah, what a lovely sentiment you have there. In Malayalam, you can say "നീ എന്റെതായിരിക്കുകയും തീരുമാനിക്കുകയും ചെയ്യുകയും ചെയ്യുക" (pronounced: nee ente thayirikkukayum theerumanikkukayum cheyyuka). Such a beautiful phrase to express your feelings to someone special.
Ennannekkum
You can say "നീ എന്റെതന്നെ" (nē eṉṯẽrtane) in Malayalam to mean "you are mine."
i am forever yours
Ennennekkumayi (ennennekkum). (e.g. My love will last for ever (forever)) Remember well that this term is always used adverbially.
Say Forever You'll Be Mine - song - was created in 1975-08.
Min for alltid (= mine forever)
dayavayi enne ennennekkum nintethakkoo...
Eien ni watashino
mine
mo cheannsa go deo
Eres mío para siempre.
Forever Mine was created in 1999.