13 DS refusing to do anything this summer

[Basilandparsleyandmint]

This is the first summer that my DS simply doesn't want to do anything. He just wants to stay in all day and play computer games and watch TV. He has a head set and just talks to his friends and is happy doing that all day every day.
I am happy to give him down time to relax as he does work hard at school.
However any suggestions of let's go swimming/ beach etc - things that I assume are still acceptable to do at his age are all rejected as a no and I don't want to go.
My DD 7 is keen to go and enjoy a trip to the park/ swimming etc so I have started leaving him at home so she can enjoy these activities as it's not fair on her.
My problems is - is this normal behaviour? He does play football for a local team and happily goes off to that.
Just the lack of motivation and not wanting to try do anything is driving me crazy.

it is common, my ds is the same. However i do force the issue, and have a rule that he can only play computer games once he has been out of the house (eg: walking to the local shop to pick up some bread, coming with me to the beach, walking the dog). If he completely refuses i wouldn't phrase it as a question. eg: come on ds, we are going swimming now. get your bag and lets go.
maybe it seems mean but to me its important that he gets out the house at least once a day

No I don' t think it's means at all.
If I do that he just stays ranting that he isn't going and makes a fuss and sulks.
Just now I said to them both come on let's go and get an ice cream. He eventually got in the car with me nagging but when we got there he refused to get out the car.
So I took his sister to get one while he sat in the car as he said his hair was a mess
I am going to start tomorrow and try and enforce each day that he does something but they way it is at the minute it's miserable.
I have removed his Xbox before but this hasn't made the impact I Was hoping for.

could you have a chat with him tonight laying down your expectation. so, tell him that he cannot get xbox time until he has left the house to be outside, starting from tomorrow. if he wines about leaving or refuses, he wont get on the xbox that day.

SO normal!!
I have a 12 yr old DD. Everything has to be bribed!!