How can I make them see me as a older brother I know we are not related ?

How can I make these boys think of me as a older brother I know we are not related the youngest thinks of me as a older brother to him just the 13 year old doesn’t really but randomly will say love you I have been in there lives for 6 years now as we needed a place to stay from a friend that worked at my moms work and we became family this is our second time living with them as the first time living with them didn’t goes as planned and her kids were distant with me for the longest time over small things I am an important part of these kids lives so I wanna be there older brother from a other mother there mom also thinks of me as a step son but this is what her response was 

You worry to much lol just let things happen naturally don’t force it cause that’s when **** hits the fan. The boys are having fun with you so don’t worry so much about it, when I said I would love to have them as brothers and think of them as brothers is this a good sign?