The key feature here isn't machines, it is libraries. Devices can only sync to one iTunes library at a time. You would have to arrange it so both computers had the same library (issues with keeping them in sync or in using at the same time), or look to a centralized service such as Match or Apple Music (with it own set of issues). The main thing is the media distributors want tight control on how music and movies can be shared (they don't care about your photos). You can do some things with Home Sharing and Family Sharing.
Family Sharing - http://support.apple.com/kb/HT201060 - "Family Sharing makes it easy for up to six people in your family to share each other’s iTunes, iBooks, and App Store purchases without sharing accounts. Pay for family purchases with the same credit card and approve kids’ spending right from a parent’s device. And share photos, a family calendar, and more to help keep everyone connected."
Sharing purchased content with Family Sharing - http://support.apple.com/HT201085 - "With Family Sharing, family members get immediate access to each others’ music, movies, TV shows, books, and apps, and can download them to their own devices any time they like.*" "* Not all content and content types are available in all countries. All family members must use the same iTunes Store country or region. Music, movies, TV shows, and books can be downloaded on up to 10 devices per account, five of which can be computers. Apps can be downloaded to any devices the family member owns or controls.
If you don't see your family's shared content - http://support.apple.com/kb/TS5449 Also: http://apple.stackexchange.com/a/146077 - quit iTunes Store and App Store apps and start again.
Which purchased content can I share using Family Sharing - Apple Support - http://support.apple.com/HT203046
Leave Family Sharing - http://support.apple.com/HT201081
Home Sharing Support page - http://www.apple.com/support/homesharing/
iTunes 12 for Mac: Use Home Sharing to import items from another iTunes library - https://support.apple.com/kb/PH19614
iTunes: Setting up Home Sharing on your computer - http://support.apple.com/kb/HT4620
Understanding Home Sharing - http://support.apple.com/kb/HT3819