Love is, apparently, really, really blind in Tyris. A relationship is possible (just to name a few) between a man and a woman, a man and a man, a hermaphrodite and a dog, an undead monstrosity and a godless killing machine, or a living rock with a cosmic horror.
You can increase your friendship with a companion by having it do battle alongside you, having it eat food mixed with a love potion that you made, as well as giving it engagement rings and necklaces. Trying to take away a companion's engagement jewelry will probably result in them destroying the item by eating it, and their relationship level with you will drop a lot. It should be noted that marriage with more than one pet at a time is possible and will not cause any negative effects.
In order to marry a companion, they must be at Soul Mate impress level and full attract level. Getting them to Fellow at roughly 150 impress is not high enough. Marriage also results in receiving a set of gifts. These include a potion of cure corruption, 2-4 platinum coins, equipment, and sometimes usable items (leash, fishing pole, etc).
|Relationship Level||Impress Points Needed|
|Foe||15 or below|
|Normal (starts at 50)||40-74|
|Fellow (shows up as (???))||150-~199|
|Soul Mate (shows up as (???))||~200-299|
|*love* (shows up as (???))||300 or above|
You create a gene by selecting the "let's make a gene" dialogue option after you reach the sleepy state.
(Note that this means going to sleep without the use of a bed. You can use this as a means of bedless sleep in dungeons, but you miss out on better dreams and potential bonuses.)
Much like relationships themselves, there are no limits, besides needing to be married, to what you can have a gene with. Feel free to breed with your bell/android/golem/whatever. Who you do the deed with, their gender, or if they are even organic life forms with genetics to pass along in these so-called "genes" to begin with doesn't matter in Elona.
Once you get a gene, you have the option to start over as your child, allowing you to inherit your current character's inventory, materials, and some bonuses. Note that precious items, kitty banks, Figurines, cards, deeds, and Small Medals can't be inherited. (coffins of necromancy can be inherited along with any living weapons)
You should probably temporarily loot your pets for their godly and miracle equipment and be sure to pick up any such items out of any static dungeons or properties you are storing them in when you are ready to make a gene - only your inventory matters.
Presumably because it would be far too difficult to work out the mechanics of what a golem-android hybrid would be like, you go through exactly the same character creation process as a completely new character would. Apparently, the golem and android can make a Yerles or a fairy as offspring. Who knew?