Hi everyone, hope everyone is safe and okay. I'm the host of my system and I'm having a few issues with an alter that shares the system with me, the issue being:

I'm currently engaged with plans to marry and live together with another person from outside the system, and all 5 alters inside it have an agreement (actually it's an article of what we call a constitution of said system, that establishes what we can and can't do) with said person that for several reasons, I'm the only allowed to maintain any romantic relationships with people from outside the system (i.e people outside the system = my wife). My wife is well aware of how we are a system and has met three of us already.

But I'm having a specific issue in which I have a coworker who clearly has a crush on me and is not very subtle about it. It so happens that one of the alters that usually fronts whenever I'm not around is crushing her back. He is aware of the agreement we all have, how it probably won't change, and has agreed to it, but still, I noticed it's having a negative effect it's having on the system.

Since I usually co-front with him, I noticed how often he wants to spend time with her, how he wants to talk and sit next to her, and even daydreams about her, something that clearly won't work because I let him co-front with me so I don't get overloaded with work finances family everything else. I noticed this because when I front alone, I tend to be more closed off, only talk to her about professional or more abstract matters and never prolong any conversation, and I actually judge her a bit, but whenever he's fronting I usually keep an eye so he doesn't flirt with her.

So with all that considered, I need some advice on how to deal with this situation, considering that the option/idea of giving him permission of maintaining his own relationships outside the system would lead to several problems and may even destroy my own marriage in the long-term, but I also don't want him to suffer that much over a girl he barely knows outside of work and will move to another country by this year's end to live with her boyfriend (She's planning to get engaged herself, btw, which adds another intrigue layer to this whole plot).

Any advice is welcomed, thanks for the attention.