Crossover #3 -- Teen Wolf (TV) x Criminal Minds (US TV)
Criminal Minds canon for Spencer Reid from ages 22 to 28 or 29, so circa Season 6.
Divergence from canon begins with a Hotch/Reid pairing following s03 e14 (Damaged). Thus, they have been dating for about 1.5 years when s05 e01 (Nameless, Faceless) takes place.
Spencer is still shot just above the knee and is disinclined to remaining a Field Agent, so decides he will only do field work to find Foyet, the bastard.
They are a little faster this time, but Haley still dies, and either Spencer or Hotch kill Foyet.
Hotch is offered early retirement in s05 e09 following Haley’s death, and after conferring with Spencer, they decide to take it.
They move to Beacon Hills with Jack and buy a nice new house on the edge of the Preserve with the Hale’s blessing.
Hotch goes back to prosecution for the County Seat. Spencer begins teaching Chemistry at BH High School. They both still consult for the FBI occasionally, and it is it their (unofficial) job to work on the Supernatural Cases that come out of BH regularly.
They are both still Liaisons with the Supernatural-Hunter Council.
They have weekly or bi-weekly Skype calls with their old team at the BAU. Spencer specifically has a standing Skype date with Henry every Sunday afternoon, and they visit every few months to catch up in person and spend time with the kids.
All this has passed, and now it is 2011.
Stiles and Scott are 15 and love having Spencer around all the time, even if that means he has to teach them at BHHS.
Since the boys adore spending time with Jack, Hotch and Reid take full advantage of this whenever possible.
Both boys have keys to the Hotchner-Reid house, so do Melissa, Noah, and Peter. The same can be said of the couple and the other residences.
The Hale Kids — Cora, Derek, Malia, and Jackson — are all excited that Spencer has moved home to BH with his family, and warmly accept Jack and Hotch into their Pack Bonds, where Spencer already has a place.
Peter, specifically, is very pleased that his best friend Spencer Reid is always around now, especially since a single-father of 3 is difficult.