It's not built in because picking two at random and having them both be compatible is not only extremely unlikely, but kind of a niche case. If you're going for certain IV spread and shiny, then you'll have two natures avaliable to be shiny, so you can look what your nature pair is, otherwise, looking for two random spreads that you would want is highly unlikely, and to my knowledge, nonexistent. If you can script, a tool to quickly check compatibility for two PIDs would probably only be a few lines.

Jan 8, 2018 - It's not built in because picking two at random and having them both be compatible is not only extremely unlikely, but kind of a niche case. DPP / HGSS RNG Manipulation Guide Part 4 - How to Abuse for your Desired TID/SID. How to Hatch Perfect Pokemon; DPP / HGSS RNG Manipulation Guide Part 4 - How to Abuse for your Desired TID/SID. Pandora's Box is bugged in version 9.94-9.95. Therefore, download the latest version before attempting this.