The less you see your brother/sister the more you actually miss their company, yes it may be annoying at times but there are those times (rare) where you enjoy their company, even just knowing their in the same house as you can annoy you but when they arent their and its just you and your mum and dad the more you realise how much you actually need them the more you realise you love them and when they start dating thats when you realise the more you care about them the more you love them the more you wish someone else isnt taking up your spot in their heart. Then you get sad/ depressed why? Bc you care and love him/her if you feel like that or do its called love, love is a strong word which is why its so close to hate, hate your brother/sister its bc you actually love them even when you dont wanna admit it...