I have read recently of an example where a father and son were killed in the same battle. The son was a drummer boy and the father an NCO, father was killed and son mortally wounded while going to his fallen father. I believe the battle was Chickamauga.
Another case was a Drummer boy wounded and cheering on his comrades in their attack. His father or older brother went looking for him the next morning and found him dieing... both of his legs had been shot away. But there were tournquits on the wounds and he had a second canteen next to him. When he was asked who had given him the second canteen he pointed to his "sleeping friend." A
CS soldier who had been disembowled... he had crawled fifty feet or so to tourniquit the boys legs and gave him his water. There were angels out there.
There are several cases where you will find family members in the same comapny or Regiment. One Company of the 1st MN that was mauled at Gettysburg cost a small town in Minnesota all but three of it's young men... the town did not survive the war.