What's the Name of That Book??? discussion

I read this sometime between 2000-2012. It's a ya fantasy novel.
A girl is becoming the queen and has to have a giant battle near the end of the book. She has a friend who is a newish wizard. He has a big accident, possibly with lightning, that almost kills him. He is taken to the dungeons/below the dungeons to heal from the earth. His skin slips off and joins with the mud on the ground to be healed. During the big battle, the girl is losing/thinking she needs help. He wakes up suddenly, healed, and goes to the top of the castle and uses super powerful magic to save everyone. At some point she has the distinct thought that he is naked and using magic. The two end uvp getting married and having kids. In the prologue for the next book, one of their kids, a son, is gettid,ng into dark magic.
I think the girl's family crest, or the name of the book, or her nickname is something to do with lions.

Sounds a bit like The High King's Daughter or possibly a Shannara(Terry Brooks)?

No, neither of those.

It's also the first book in the series. But the series only had two books when I read this book.

Figured it out! "The Cry of the Icemark" by Stuart Hill.

Glad you found your book, Cairhys. Here's the link - The Cry of the Icemark by Stuart Hill.