Although it's the policy, I don't think they'd enforce it because AFAIK they are talking about adult 3rd person. We just concluded a 6-night stay where we had two rooms with 2 adults in one and one adult with two children in the second room. We were all welcomed to the M-lounge without issues as this is NOT a nickel and dime you property, in my experience. If you have any issues, ask for Ms. Jiap, the lounge manager, she is very accommodating.