If you are legally married and living together then you can only file as Married Filing Jointly or Married Filing Separately. You should file a MFJ even if one spouse has little or no income. All income for both spouses is entered on one tax return when filing Jointly.
You can Never claim a spouse as a dependent when you are married.
If you are filing Married Filing Jointly, then income from both of you needs to be included in the return.
However, if you filing as Single or Head-Of-Household, and claiming your significant other as a Dependent, their income is NOT included in your tax return. You can only claim another person as a dependent if they meet all requirements for the dependency test - age, income, and relationship tests.
If by "significant other" you mean a GF or BF, then no, you do not enter their income on your own tax return. We need clarity---are you legally married or not married? If you are not married and want to claim an adult dependent----they must meet the criteria to be a "qualifying relative"
Did the "significant other" live with you for the entire year in 2022? Did they have less than $4400 of income in 2022--not counting any Social Security? If the criteria to claim them is met, you get the $500 credit for other dependents when you claim them.
CREDIT FOR OTHER DEPENDENTS
The only time you report someone else's income on your tax return is if you are legally married and filing a joint return. If this is your unmarried partner, they file their own tax return for their own income, even if they qualify to be claimed by you as a dependent. (I will assume they do meet the qualifications, we can discuss this separately if needed.)
Assuming your partner qualifies as your dependent, they must have less than $4400 of total taxable income (wages, lottery prizes, self-employment from side gigs, and so on). In this case, they would not be required to file a return at all**, unless they had tax withholding and want it refunded.
(**If the person is under age 19, or a student under age 24, their parents are alive, and they have more than $1100 of unearned income--which is to say, income not from working but from investments, gambling, unemployment compensation, and so on--then they may be subject to the "kiddie" tax and may need to file a return.)