You can try fanfiction websites like Archive of Our Own (AO3). Just go to the site and use the search bar to type in 'Pack Mom Stiles baby Liam'. There might be some great stories there.
Fanfiction.net could also be a good place. However, the search function might not be as refined as AO3. You'll have to dig a bit deeper sometimes. But if you're persistent, you might find some interesting fanfics related to Pack Mom Stiles and Baby Liam.
One common theme is protection. Stiles often takes on the role of protecting Baby Liam, just like a mother figure would. It shows their bond in a very endearing way.
The pack mom's relationship with Baby Jackson could be one of nurturing and protection. She could sing lullabies to him that have a hidden supernatural meaning, which only Jackson can sense. As Jackson grows, he starts to see the pack mom as his main source of comfort. And this relationship could also influence how the pack as a whole views Jackson. If the pack mom shows strong affection for him, it could make the other pack members more accepting of the baby, who might be different from them in many ways.
A possible plot could involve the pack mom trying to raise Baby Jackson while Stiles acts as an unexpected mentor. Stiles, with his quick thinking and knowledge of the supernatural, helps the baby develop in a way that surprises everyone in the pack. For example, he might teach Jackson how to control his emerging powers at a very young age. This could lead to a series of adventures where they all have to face different challenges together, like fending off other supernatural beings who are jealous of Jackson's potential.
The relationship between Pack Mom and Isaac could develop through acts of care. For example, Pack Mom cooks for Isaac, helps him with his homework if he's still in school in the fic. This makes Isaac trust her more. Stiles and Isaac's relationship might start with Stiles being a bit wary of Isaac as a new addition to the pack. But as they go on adventures together, like facing a minor werewolf problem in the neighborhood, they become closer friends. And as for Pack Mom and Stiles, they could have a deeper bond as they both care for Isaac.
One idea could be that Pack Mom takes in Isaac when he's injured. She nurses him back to health and in the process, Isaac starts to see her as a mother figure. Stiles is initially jealous but then realizes how much Isaac needs that maternal love. Another plot could involve a threat to the pack where Pack Mom, Stiles and Isaac have to work together to protect the others. Isaac discovers a new power during this time which helps them in the fight.
It's popular because it gives a new and interesting dynamic to the character of Stiles. Instead of just being the sidekick, he becomes a central figure of care and support in the pack.
Fanfiction.net could also be a good place to look. There are many different fandom - related stories on this site. Just search for Ruby and Liam with the addition of 'baby' in the search bar to narrow down your results.
You can start by looking on Archive of Our Own (AO3). It has a large collection of Teen Wolf fanfictions, and you're likely to find many Stiles knows the Alpha Pack ones there. Just use the search bar and type in relevant keywords.
One great story could be 'The Pack Mom's Guidance'. In this fanfiction, Stiles takes on the role of pack mom in a really heartwarming way. He looks after the pack members, making sure they are safe and happy. Another good one might be 'Stiles: The True Pack Mom' where he uses his intelligence to solve pack problems like a mother would for her family.
In many 'female stiles pack mom fanfiction', the theme of sacrifice is present. She may have to sacrifice her own desires or time for the well - being of the pack. Also, the theme of acceptance is there. The pack has to accept her in this new role and she has to accept the responsibilities that come with being the pack mom. There are often storylines where she has to earn the respect of some of the more skeptical pack members, which makes for an interesting read.