IS IT WRONG TO MISS A DEAD FAMILY MEMBER YOU'VE NEVER MET?

[Alert Wolf]

my mom started lecturing me about how i joined a SIDS "support" group on facebook "with a bunch of strangers who could really be murderers" (according to my mom) my cousin died of sids when he was 7 weeks old 20 (almost 21) years ago and i'm only 16 so i never met him but i miss him and aparently i'm "taking on the greif of my aunt, uncle, and cousin" (again, according to my mom) my mom just doesn't understand; my old karate dojo was practically next door to where he died AND we live in the town of the hospital he was pronounced dead at (i've probably passed that hospital a million times since i've been here) AND i'm super close (to where we're twins) with his sister
she just doesn't understand, am i wrong to miss him?
btw its not really a support group, i mean, it kinda is but not legitimately she just keeps calling it that