ok, so I started a new job 8 weeks ago today and another new guy started about 2 days after me.
Working hours for both of us were stated as 9-5.30.
It is a very small office (9 of us including me and said guy, but only 5 of us work together in the upstairs office)
It's a very relaxed laid back working environment. 2 bosses that share the business equally. I report into one of the bosses, he reports into the other (2 separate areas of the business)
Both bosses are mostly out of the office at meetings or working from home so we are mainly left to get on by ourselves.
There should be no issues with this as we both have plenty of work to get on with, know what we are doing etc and we could call our bosses if we needed anything.
The first few days was fine, but 2 weeks in he started taking the piss a bit.
He doesnt drive so his wife has to drop him off and pick him up, but they live 5 mins drive from the office.
Every day he slopes in at 9.10-9.20 and calls his wife to pick him up anytime between 5-5.30
He also doesnt have a mobile phone so uses the office phone several times a day to call his wife/family/book weekend activities etc (His wife also calls the office to speak to him at least twice a day)
He smokes quite alot and goes out for a cigarette break several times a day, roughly one fag break every 1.5 hours (not sure if that's normal as I have never smoked so dont know what is considered acceptable!)
He sits next to me so i can see exactly what he's doing on his screen all the time - and 9 times out of 10 he is on facebook, looking through pictures or writing private messages to people.
using FB in office hours is not exactly frowned upon though, as we do a lot of business through it, and my role genuinely requires me to be on it a fair bit. (As well as MN 
)
However, he works for a different part of the business, (our sister company I suppose you would call it) and there is no reason to be on FB at all for his role.
The other person in our upstairs office has noticed this too, but she already had a bust up about him stealing her sales (they are both commission based) so I think she is reluctant to say anything for fear of making things any more awkward
When his boss is in, he does his job (basically calling companies from our database and trying to sell things over the phone) but because his computer is turned the other way, I can see he is still on FB as he knows his boss can't see
So, what I'm asking really is AIBU to 'grass' this guy in?
I know it's not really my place and its not that I'm pissed off that I am genuinely working and arriving and leaving on time, its more that I'm angry that he is taking the piss out of this small family run business that the 2 bosses have worked hard to build from scratch.
So, should I say something? I don't want to come across a snitch or make my boss think I'm a twat but he's winding me up big style with his piss taking
TIA