This is a question often asked by newlyweds: After marriage, does a good or bad credit rating of one spouse affect the other spouse?
The answer is that one spouse does not affect the other spouse directly. You continue to maintain your own credit rating and credit history regardless of whether you get married or divorced (and is also not affected by a name change after either event.) Credit that has been taken out in your name alone goes into the making of your individual history.
However a spouse's rating can indirectly affect you, by affecting your ability to establish a joint liability. For instance, suppose you want to take out a joint credit card or a mortgage. If one party has a poor credit score it might affect your rate. In this circumstance the spouse with the better score could take out the loan in his or her name alone.
Something else to consider is why one spouse has a low credit score. Does that person have poor credit habits, making payments late or building up a lot of debt? In this case you might want to keep all of your credit separate. Both parties on a joint loan are liable for the debt, regardless of who is responsible in your eyes for making the payments, and it affects both your credit scores.
On the other hand, taking out a joint loan and making sure you stay current may be a way to help the spouse with a poorer score to boost his or her numbers.
It is important for both spouses or partners to be upfront and honest about their credit history. It could affect your ability to save together for retirement, vacation, or other goals.