Personally I wouldn't do it - I had the same dilemma with my boys as I had used my absolute 2 fave names for DS1's name (and in hindsight, I actually preferred his middle name and wished we had used that as his first name) but I just couldn't use it again - probably no logical reason other than it didn't feel 'right'.
I am a bit confused though as to why you can't use Andrew as a first name for this baby??
Bad idea IMO you could end up with the first child feeling like you felt he wasn't good enough for the name being that he only got it as a middle name and also that the 2nd one 'stole' his name, bit like taken part of his identity.
I wouldn't do it - the second DS may feel that as his name was only your second favourite that he too was 'only' your second favourite!
DD1's middle name is Mary. We didn't consider it as a first name when we named her but I'd always wanted it as my DD's middle name in honour of my Grannie.
When pregnant with DD2 we seriously considered Mary as a first name for her. Partly because both DH and I loved the name but also because my Grannie had died. We felt we couldn't call DD2 by DD1's middle name as she may feel less special (she was 4.5 when DD2 was born). Then we came across the name Miriam; a version of Mary and a name we love (even more so when we discovered one of the meanings was 'wished for child') so DD2 is Miriam.
My DS1 is James Alexander and my DS3 is Alexander. There were no other names that I loved as much as Alexander - in fact it is my number one favourite name but James is my dads name so I went with that for my DS1.
Considering how little middle names are even heard I had no problem re-using DS1's middle name. Alexander is also my DH's middle name so my DS's just think of it as a family name and that it's a nice connection for them all, iykwim.
I wouldnt purely because a friends DH was a late in life baby at least 10 years between him and siblings. Older brothers name Paul Adrian, younger brother then called Adrian Paul. Just feels like parents couldnt quite be bothered to think of something new and original. If it was me I would always feel a bit crap about it I think.