Does this mean that the brother was later, or someone is saying "later" to their brother?
Check on dictionaries, later is different from latter, latter mean as follows:
adjective 1. situated or occurring nearer to the end of something than to the beginning. "the latter half of 1989"
- denoting the second or second mentioned of two people or things. "the Russians could advance into either Germany or Austria—they chose the latter option" synonyms: last-mentioned.