For such a cousin, I don't think you need to be stingy with your lipstick, but if you like this lipstick very much, you can also discuss with him and give him a lipstick that you don't need and don't use often, so that you can keep what you like. And it can increase the affection between you and your cousin,
Many people think that they can't give their things to others, but this idea is often wrong. You can think of it this way. If something you don't use often is especially liked by others, why not give it generously to others? In this way, the feelings between others and you will be much stronger.
Besides, you can use something you don't often use to increase your relationship with your relatives or friends. Why not? In addition, I feel that with the rapid economic development, nothing is particularly precious. Even if you and your cousin go to the countryside to play, your cousin will definitely give you something you like and take out their best things to entertain you at that time. This is a normal phenomenon of secular communication.