Q. Does a grandfather recite a Shecheheyanu when seeing first time his great grand son?

A. Biur Halocho (223: 1) debates whether a brocho should be recited for the birth of a
grandson since he won’t necessarily provide the aid, help and service that a son would.

K’tzos Hashulchan (64) maintains that the first time a grandfather sees his grandson, he should recite the brocho as one would in principle when seeing a friend after a while of separation. (See Piskei Teshuvos 223 n. 15).

Horav Shlomo Miller’s Shlit’a opinion is that in principle he can as his joy is great, however, it is better if he also eats a new fruit of that year or similar.

Rabbi A. Bartfeld as revised by, Horav Dovid Pam, Horav Aharon Miller, Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit’a