It depends. Most operators that is fine. Claim both tickets in one transaction.
XC on the other hand make it as difficult as possible! I was on a delayed journey with the kids and they rejected the claim for four tickets saying they’d need to speak to all four of us to make sure. I emailed back to say youngest child was 5, I was Deaf, middle child was Deaf, so good luck phoning us.
They backed down in the end and paid out the £5.20 total to me!
Don't think Network Rail would be interested. It is LNR you hopefully contactedLNWR