Apparently so, since he had a mother-in-law. Customarily the two go together. Sometimes they even remain together, both staying in a fellow’s home. This has been the source of many jokes and sad tales, none of which need be recounted here. Instead, let’s consider Matthew 8:14-15 and Luke 4:38-39, which say that Peter’s mother-in-law was sick with a fever. Jesus rebuked the fever. It left her, and she got up and served him and his companions.
What about Peter’s wife? She is nowhere mentioned. I find this strange. Imagine the scene. There is the mother-in-law, lying in bed. At her side, as one would expect, is her dutiful daughter—except that Matthew and Luke make no reference to her daughter. Leaving her out of the story is strange. It is not the way a writer would be expected to handle the incident, since a daughter usually is the one most frantic about a mother’s condition. The story is tantalizingly brief. Maybe the Evangelists decided to leave out all but the most salient facts. Or maybe it was because Peter’s wife wasn’t there—she already may have died. I think this is the most likely explanation for her non-appearance.
Those who disagree cite 1 Corinthians 9:5: "Do we not have the right to be accompanied by a wife, as the other apostles and the brethren of the Lord and Cephas?" (RSV-CE). This suggests that in his travels Peter (known as Cephas) journeyed with his wife. The issue is whether the RSV-CE and similar translations are correct. Should the underlying Greek be rendered as "wife" or as something else? I think the stronger case is with the something else.
In this passage Paul defends himself and the other apostles against charges from a few disgruntled people. He says he is giving "my defense to those who would examine me" (1 Cor. 9:3). He talks about a situation that applies to himself, not just to the others, yet he certainly was not accompanied by his wife, since he had no wife. We know from other testimony of his that he was unmarried. He does not speak of a theoretical marriage, one that he might someday have but does not yet have. He responds to complaints concerning whichever women actually did accompany him and his male companions. This indicates to me that "wife" is not the right translation here.
The key Greek words in 1 Corinthians 9:5 are "adelphaen gunaika." The first means "sister," and the second can be translated as either "woman" or "wife." This means the phrase translates as "sister woman" or "sister wife," with "sister" indicating not a biological but a spiritual relationship. It would make sense for the apostles to be accompanied by "sister women" who could assist them in ministering to women—for example, at full-immersion baptisms, where a question of modesty could arise, or in cases where it would be more appropriate for a woman to perform a charitable or catechetical function.
This finds support in the Fathers. "Sister woman" is found in Jerome’s Vulgate, and Jerome wrote that "It is clear that [they] must not be seen as wives but, as we have said, as women who assisted [the apostles] with their goods" (Ad. Jovinian I, 26). Clement of Alexandria agreed, saying the women were not the wives of the apostles but were female assistants who could enter the homes of women and could teach them there (Stromata III, 6).
In short, I think Peter was a widower at the time his mother-in-law was healed.