I can't believe some posters are suggesting the OP is jealous. It's clearly the parents of this lad who are jealous. Jealous and competitive.
Me and DH have experienced people like this in our lives since we have been together (over a quarter century!) People who copy what we do in the garden, copy our decor, copy where we go for a meal, copy our hobbies, and even do stuff like get a new 3 piece suite or a new set of dining table and chairs when we get one (even if theirs is only a year old - yes really this has happened!!!) and I have even known one couple who kept booking a holiday to the same place as us. 
This one couple (neighbours) were a fucking nightmare for this a few years back... When DH told them we were going to book a trip to Canada for our 20th anniversary (some 4 or 5 years back,) I could have fucking screamed at him, as I knew they were going to copy us, and book a trip there too.
Sure as eggs is eggs, within DAYS, this couple had booked a trip to Toronto. I refused to go then, and said I want to go to South Africa instead, and go to Canada another time. So we booked a trip to S.A. for our anniversary, and didn't tell them until 3 days before we went. She went flame red and said 'South Africa? I thought you were going to Canada for your 20th anniversary!' with a kind of
look.
'NOPE' I said, 'we changed our minds.' She was fuming and really angry that we switched where we were going God knows why! What the fuck did it have to do with HER?
Stupid cow went and booked a trip to South fucking Africa a few weeks after we came back for the following Spring! 
This couple, by the way, legged it last year in the middle of the night, and their house came up for sale as a repossession. Seems their 'trying to keep up with the Joneses' caught up with them!!!
But yeah, the couple the OP is on about sound the same. Jealous and competitive and weird, trying to outshine what the OP is doing.
@BuffyBee I have to agree with the posters however, who are saying there is nothing you can do about it. They are just making themselves look pathetic. The more you tell yourself this, the less it will bother you.
I disagree though with the posters who say imitation is the sincerest form of flattery. No it's not; it's fucking weird as hell, and makes you look like a stalker.
If it bothers your son, buffybee he may have to start giving this lad a wide berth.
I also think the people who say you are being unreasonable are the type who do exactly what this lad's parents are doing LOL!