Because my husband died can I claim one of my dependent sons as equivalent to spouse?

I'm sorry to hear of your loss. 

You may be able to claim the amount for an eligible dependant if you met all of the following criteria at the same time during the tax year. Once you claim this amount for a dependant, no one else is allowed to claim this amount for that dependant, or the amount for an infirm dependant for the same dependant.

• You didn't live with a spouse or common-law partner.
• You didn't financially support or receive financial support from a spouse or common-law partner.
• You supported a dependant who was one of the following, and
  • Your parent or grandparent by blood, marriage, common-law partnership, or adoption, or
  • Your child, grandchild, or sibling by blood, marriage, common-law partnership or adoption and under 18 years of age. If the dependant was older than 18, they must have had an impairment in physical or mental functions.
• Your dependant lived with you in a home that you maintained (in most cases in Canada). You cannot claim this amount for someone who was only visiting you.

Please see this TurboTax Canada FAQ to see how to claim the eligible dependant amount: How do I add or remove the amount for an eligible dependant from my tax return?