As Herbert said, when a merge is done, the ancestors / parents should always be merged first. I have proposed the merge of the mother now, also. Since you have the Pelletier profile 'locked' somewhat, you will be the only one that can complete the merge, once the other person, looks like a half or full brother, has approved the merges.
Merges go into a 'default approved' status after 30 days if one or both PMs have not approved the merge. At that time anyone can complete any merge, as long as both profiles are unlocked.
When a merge is done, the biography is normally merged together and a little cleanup is needed to remove any duplicate text that was taken from both profiles. As Melanie said, merges are a little 'scary' initially, but that is OK. It is better to be cautious doing a merge to make sure that they are being done correctly.