I realize that this question is a few years old, but I am answering it in attempt to help any one else who may be in a similar situation.
I am unsure how you determine who owns how many 12ths of the house. Look at your deed first. If the deed is a joint tenants with rights of survivorship (JTWROS), then each person owns a 1/2 interest in the property regardless to the contribution to purchase price. If the deed was taken as joint tenants in common (TIC), then each person owns a share in proportion to the amount he contributed to the purchase price. If the property was inherited, the shares probably are equal unless otherwise stated.
When a property is held jointly, each tenant (or owner) has a legal right to file a partition to petition with the court. That means that either the property will be sold and the proceeds will be distributed according to ownership shares, or one owner could buy out the other person's share. The fine details on real estate partition laws vary from state to state.
Before you jump into a partition process, please think of the following ----
1. Partitions can be very costly, particulary if you encounter an stubborn participant and if you are disputing the shares of ownership.
2. Partitions can be very lenghty. Don't expect to "force" a sale quickly.
3. A forced sale usually brings much less than a normal sale.
4. Partitions normally signal the end of a relationship.
5. Once you file for partition, you totally lose control of the property. The court is in control of the property.
My suggestion. Try to work this out before jumping into a partition.
Warning: partitions can be harmful to your health and ot your pocket book!