Can anyone explain this behaviour please?

[Megibo]

I have a 16 month old dog, about half an hour ago my older sister came flying into the kitchen really screaming and shouting in a rage. He cocked his head at her as though trying to figure out the feelings he was getting from her and watched while she shouted at my little sister. However when I went to walk forwards he looked at me and then used his bum to back into my knees and push me backwards and wouldn't let me go past him until my older sister had left the room and gone back upstairs. Once she left he relaxed and happily let me go past him. Ideas?

He is a Rottweiler and perhaps closest to me as I've spent most time with him and taught him what he knows/have most cuddles on the sofa with him ( )

 

[CorvusCorax]

Could be a combination of feeling the need to protect you or insecurity/leaning on you for support, more common than you would think.

While it may seem cute/admirable, you do not need 'protecting' from family members and neither should he....he perhaps feels forced into this role because you were passive...if there are fights/raised voices again either remove him (apart from anything else, it is stressful and not productive to expose a dog to this) or remain quite assertive and confident so he neither feeds of your insecurity or feels the need to be insecure himself - with a large breed dog such as a Rott, if you force them into the role of protector when it is not warranted (general family barnies), you end up with problems down the line.

 

[Megibo]

Could be a combination of feeling the need to protect you or insecurity/leaning on you for support, more common than you would think.

While it may seem cute/admirable, you do not need 'protecting' from family members and neither should he....he perhaps feels forced into this role because you were passive...if there are fights/raised voices again either remove him (apart from anything else, it is stressful and not productive to expose a dog to this) or remain quite assertive and confident so he neither feeds of your insecurity or feels the need to be insecure himself - with a large breed dog such as a Rott, if you force them into the role of protector when it is not warranted (general family barnies), you end up with problems down the line.

Exactly, when she came towards me he really tensed up and I said to him 'ah-ah' and he cocked an ear back but remained where he was. It is not often we ever have moments like this and we don't want to encourage any guarding behaviour whatsoever being the breed he is.

 

[CorvusCorax]

Try standing in front of him, the way he was bodyblocking you, do the same to him...it may sound alarmist but you don't need to be defended from your own family members, ideal scenario is remove the dog from the room if you all are having a moment, dogs are not robots and they do pick up on stress, tension etc. Me and my mother fight the bit out but we try and do it in another room from the dog

 

[CAYLA]

I think the initial head cocking was possibly her high pitched shouting/screaming.
But as a breed that does commonly display protective/guarding traits to those they have bonded with he may well have sensed a threat coming from your sister, either that or he himself was feeling insecure and asking for reassurance and as CC suggests be careful not to encourage this behaviour otherwise he may well become a little to protective in circumstances you really would not want it
If my OH starts playing with my rotti she often back up into my legs and wriggles about, this is her asking for reassurance but she also intervenes when we play fight together in this instance she stands across me with her body not just wiggling her bum into me like she does when they play together and she stands rigid not wriggling movements like when she is playing and this is her guarding/protective stance. Body language is always a good thing to be familair with in regard to your dogs behaviour.
Have we had any pictures of this lovely boy??