ML loves his childhood friends 'sweetheart', and his internal dialogue/struggles with this, are very enjoyable to read. He recognizes pretty quick he is in love and that it is an issue, so tries to distance himself from FML (MC), as he cares for his friend a lot.

He even tells his family, to 'sell' him off for marriage (to whichever family is most beneficial), so he can get over/away from MC. And some of his internal dialogues during this are great, like when he is thinking about what a loveless marriage would look like, how he should find someone who doesn't love him, and how he doesn't need children (2nd in line), but he wonders what it would be like to have a child with woman he loves, vs one he doesn't... And this sets up the 'intro synopsis' scene nice, because apparently he will be Heir to dukedom (so his bro must die, and he must have to produce an heir now) - and because he now has to produce an heir, he'll likely want it to be with someone he loves as he's already thought about children born out of love vs not... so it's just setting it all up nicely, even with the internal dialogue.

Meanwhile, the FL is not 'romantically' in love with the childhood friend/fiance. She says yes to the marriage, because she is all alone (no family - maternal figure just died too), and childhood friend 'understands her' the best. A nice twist, is she actually gets nervous/excited around ML, pretty early on, so it sets up this nice drama between the three. She doesn't recognize it as 'love', but we as readers do, so it creates some interesting suspense of 'when will she notice her feelings' and how will that impact those 3's relationship. I liked that, cause I wasn't expecting that, and it sets up a lot of potential drama. Also makes the MC ML pairing more romantic imo. Would've been good either way tbh, but now rooting for MC more than I likely would have.

I don't feel super bad for 2nd ML, knowing what is coming. Ofc he doesn't deserve it! I'm just not getting 2nd ML Syndrome, which is nice. Because we know FMC doesn't love 2nd ML romantically (yet?), even after he is very very clingy for months, when she has literally no-one else to support her emotionally/financially. He also knows she does not see him as a man, and he also knows going to propose marriage, right after her maternal figures death (his grandma), is manipulating her emotional state because she has no-one else to rely on, so she is likely to say yes for that reason (not for Love). So it's not a very 'romantic' marriage where she's marrying for Love. But he is, obviously. I'm not dogging on 2nd ML, I'm just saying you probably won't get huge 2nd ML syndrome, even though he is a nice guy.

2nd ML is also somewhat shown to have a bit more of an 'immature' love towards MC, while ML is a bit more mature/responsible. But 2nd ML is potentially changing. For example, ML starts questioning 2nd ML about how he is going to marry her, as she is a commoner and he is a noble. He says the first step, is to get her (MC) to like him. And he's been visiting her A lot, EVERY day, to get this to work. And ML is annoyed at 2nd ML, telling him he's got to think long term, and start working on protecting her now, not when it's 'necessary'. And this shows as MC doesn't feel comfortable telling her issues to 2nd ML, as she feels she has always been solving his problems, and doesn't see him as a reliable support figure, and she also doesn't want to 'burden' him... But she sees ML as reliable support.