If the Torah tells us to love the stranger, וַאֲהַבְתֶּם, אֶת-הַגֵּר is there a command to love one's husband/wife?
The Gemara in Kiddushin (beginning of the 2nd chapter) takes it for granted that the Mitzva of וְאָהַבְתָּ לְרֵעֲךָ כָּמוֹךָ - love your friend as yourself refers to one's spouse, which is why it is forbidden to marry somebody before seeing them.
אסור לאדם שיקדש את האשה עד שיראנה שמא יראה בה דבר מגונה ותתגנה עליו ורחמנא אמר ואהבת לרעך כמוך
BTW there is a Rabbinic commandment to love ones wife as oneself (some people explain that it means not more then oneself(since there already is a commandment to love all Jews))
It is brought in the Rambam ishut 15:19
Similarly, our Sages commanded that a man honor his wife more than his own person, and love her as he loves his own person....
The Rambam's source (acording to magid Mishnah) Talmud Yevamot 62b
About love Rambam De'ot 6 Halachah 3
Each man is commanded to love each and every one of Israel as himself as [Leviticus 19:18] states: "Love your neighbor as yourself." Therefore, one should speak the praises of [others] and show concern for their money just as he is concerned with his own money and seeks his own honor.
Loving a convert who has come to nestle under the wings of the Shechinah [fulfills] two positive commandments: one for he is [also] included among the "neighbors" [whom we are commanded to love] and one because he is a convert and the Torah (Deuteronomy 10:19) states: "and you shall love the converts.".
[Thus, God] has commanded us concerning the love of a convert just as He has commanded us concerning loving Himself as [Deuteronomy 11:1] states: "and you shall love God, your Lord." The Holy One, blessed be He, Himself, loves converts as [Deuteronomy 10:18] states: "and He loves converts."