Formal:
* J'aime beaucoup mon frère. (I love my brother very much.) - This is a standard, polite way to express affection.
Informal:
* J'adore mon frère. (I adore my brother.) - This conveys a stronger sense of love and fondness.
* J'aime mon frère à la folie. (I love my brother madly.) - This emphasizes a deep and passionate love.
* Je l'aime tellement! (I love him so much!) - This is a more casual and heartfelt way to express affection.
To really emphasize the "loooooove" feeling, you could use:
* Je l'aime de tout mon cœur! (I love him with all my heart!)
* Je l'aime plus que tout! (I love him more than anything!)
Remember, the best way to express your love for your brother depends on your personal relationship and the context of the situation.