When talking about the way the grandma does nothing, she basically ignores the youngest granddaughter when she taught both of the older grandchildren, yet it's presented in a strange way of her regretting not being able to teach the eldest bcs of her lack of hearing and thus wanting grandchildren she could teach. The eldest one has quite a bit of focus on her, which I like, but it only makes the younger ones lack of substance weird and makes a person wonder why she was even written in. Then going into the alternate life timeline, she isn't even mentioned once, as if a person who doesn't exist, makes you wonder if the author sorta forgot about her, which is somewhat laughable confirmed when every character says gb in the final AN except for her.

who was described as mostly non verbal and thus a point of fear for the MC, who was scared he might be neurodivergent or 'lacking' something

TLDR; FL after her death reborn back to her teens and went to ML. They got together. After death due to old age, ML woke up to the time he was released in prison. He helped FL move on from her ex-husband and married her. Then, that was the reason FL looked for him in the next life. Basically, it was a loop.

because her love for him died when she suffered a second miscarriage caused by the second ML's first love.

ML did fall for FL at first sight, but since it really was just almost impossible for a rich lady from the city to fall in love with him who was a poor boy from a landlord's family, he did his best to avoid and ignore her. His words to her were quite rude in order to push her away. He does get even more moved by FL after seeing her high capabilities and her openness to business. When FL confessed to him and established a relationship with him, he thought that FL would get bored with him sooner or later. But FL never left him even during his hardest and most shameful times and even supported him and loved him no matter how stinky and dirty he is, his idea quickly changed into saving for the bride price to be able to marry FL. sh*t happens

Honestly, the second ML (Jiang Jianjun) could've been ML in another novel had FL not been reborn too. Unfortunately for him, FL was also reborn and no longer wanted to do anything with him, and her heart already belonged to ML since the previous timeline. He reminds me so much of 1st timeline Emperor Ruvi from Abandoned Empress (though Ruvi wasn't reborn so he was a good ML in the 2nd timeline lol) and Duke Wislash from I Don't Love You Anymore. He loved FL too late. By the time he realized he couldn't live without FL, FL's love was already exhausted and he can no longer make it up to her (especially since she could no longer bear children after her 2nd miscarriage). Yes, he was tragic but it can't be helped. He and FL are incompatible since they both have different expectations for their marriage and their personalities clashed. I really didn't pity him since he never changed after being reborn and kept on forcing himself (figuratively) into FL's life even though she didn't want to be involved with him anymore.

In both timelines, They're meant to be together to grow, heal, and be each other's support while growing old and retaining their unconditional love coz yes, the ML was rebirthed too on the marriage life that the FL remembered or came from. On their first life, ML wasn't too sad when the FL couldn't give him a child anymore due to her twice miscarriages (due to her ex-husband's Idiocracy that'd caused her sufferings) cause the ML was very much aware that they're going to have twins on her rebirth. It actually warms my heart whenever I remember the encouragement that they tend to remind one another during their deepest and hopeless times.