How can I get my little brother to stop trying to sleep in my bed?

He's going to be ten this year, at this point it's just weird and makes me uncomfortable. It's every night now that he asks to sleep in my bed, if I say no he comes back throughout the night saying "Pleeeeeeeeease?" over and over like it's going to change anything. Many times he climbs into my bed without permission and refuses to leave. Most nights I force him out, but others my mom tells me to just suck it up and let him sleep in my bed. Isn't it weird at this point since I'm almost sixteen and he's getting too old for this? How can I get him to stop, since I lack any parental support on this? Am I just being weird, as my mom insists I am?