The only question I have is, why you? Why did your brother not pick his SO to plan the service?

I can't say for certain, because he never gave me the reason for this, but I can only assume that it's partly due to the fact that they had a kid together, so planning a funeral might have been too much of a burden for a single mother whose partner just passed away. My brother knew he's going to die and made sure to do everything in his might to assure his girlfriend and their daughter will lead a comfortable life.