Can a child be named after two different relatives?
Different families have differing customs in this regard and it is not a fixed rule. In my own family, we do not name a child after two different relatives, as the reality is that the child’s name ends up being not that of either relative. For example, if the child is named Shimon after one grandfather, and Yosef after another grandfather, he will have the name Shimon Yosef which was not the name of either grandfather.
But the most important thing is to maintain peace in the family and not turn the joyous occasion into a war between the parents or grandparents. As I began this response, we are talking about family custom and not Jewish Law. Especially if the parents know that they will not have more children and there are close family members who have not yet merited having a descendant named for them, it may be advisable to accommodate the needs of the moment.