Hi all,
We have a 7 month mini schnauzer/mini poodle cross. She is the loveliest little dog and is particularly attached to me - as I’m home every day so I do the bulk of her care. She tends to follow me everywhere and sits next to me etc. She particularly loves to lick me and my clothes.
My parents own her brother, he arrived at our house yesterday and is staying with us for 4 weeks as they’re away.
Everything is ok , however our pup is not taking kindly if her brother tries to take her position next to me on the sofa, or jumps up to be petted etc. She really grumps at him about it 
Our thoughts were to insure she always gets first dibs of my attention but I’m now wondering if that’s not going to help the situation!
I don’t know if she’s jealous, possessive of me or what? They generally get on very well, very excited to see each other, play together. Personality wise I’d say she’s a little more chilled than him- he barks a lot at noises- but other than that neither one seems more dominant.
An extra bit of info is that our pup is currently in season- her brother is castrated. He has been humping her a lot- but this is quite normal for both of them anyway, they usually take it in turns to jump all over each other 

Any tips would be great thanks!