Odysseus’ sister Ktimene is mentioned by the swineherd Eumaios but never by Odysseus. The scholia connect her to one of Odysseus’ companions. The evidence for this seems to be the fact that Ktimene was sent to Same for marriage (where Eurylochus is from) and a kinship term used for him by Odysseus. Also of interest, according to the scholion, Odysseus may have had more sisters.
Homer, Odyssey 15.364-41
Strong Ktimenê, the youngest of the children she bore.
I was raised with her, and she honored me little less.
But when we both made it to much-praised youth,
They gave her to Samê and received much in return
But she gave me a cloak, tunic and clothing
Dressing me finely and give me sandals for my feet
And sent me to the field. But she loved me more in her heart.
οὕνεκά μ’ αὐτὴ θρέψεν ἅμα Κτιμένῃ τανυπέπλῳ
θυγατέρ’ ἰφθίμῃ, τὴν ὁπλοτάτην τέκε παίδων·
τῇ ὁμοῦ ἐτρεφόμην, ὀλίγον δέ τί μ’ ἧσσον ἐτίμα.
αὐτὰρ ἐπεί ῥ’ ἥβην πολυήρατον ἱκόμεθ’ ἄμφω,
τὴν μὲν ἔπειτα Σάμηνδ’ ἔδοσαν καὶ μυρί’ ἕλοντο,
αὐτὰρ ἐμὲ χλαῖνάν τε χιτῶνά τε εἵματ’ ἐκείνη
καλὰ μάλ’ ἀμφιέσασα ποσίν θ’ ὑποδήματα δοῦσα
ἀγρόνδε προΐαλλε· φίλει δέ με κηρόθι μᾶλλον.
Schol. BW ad Od. 15.364 ex
“Ktimenê is the proper name of Odysseus’ sister, whom Eurylochus is supposed to have married.”
Κτιμένη] Κτιμένη κυρίως ἐκαλεῖτο ἡ ᾿Οδυσσέως ἀδελφὴ, ἧς
ὁ Εὐρύλοχος ὑπονοεῖται ἀνήρ. λέγει γὰρ “καὶ πηῷ περ ἐόντι μάλα
σχεδόν” (κ, 441.). B.Q.
“She bore the youngest of the children”: [this means] of the female children. For his father only had Odysseus [for a son]. There were more sisters of Odysseus.”
ὁπλοτάτην τέκε παίδων] θηλειῶν γοῦν. μόνον δ’ αὖτ’ ᾿Οδυσσέα πατὴρ τέκε (π, 119.). καὶ πλείους οὖν αἱ ᾿Οδυσσέως ἀδελφαί. Q.
Homer, Odyssey 10.438-442
“So he spoke, and I was turning over in my thoughts
As I began to draw the sharp-edged sword next to my thick thigh,
Whether I should cut off his head and drive him to the ground
Even though he really was my relative. But our companions
Were restraining me with gentle words from all sides.”
ὣς ἔφατ’, αὐτὰρ ἐγώ γε μετὰ φρεσὶ μερμήριξα,
σπασσάμενος τανύηκες ἄορ παχέος παρὰ μηροῦ,
τῷ οἱ ἀποτμήξας κεφαλὴν οὖδάσδε πελάσσαι,
καὶ πηῷ περ ἐόντι μάλα σχεδόν· ἀλλά μ’ ἑταῖροι
μειλιχίοισ’ ἐπέεσσιν ἐρήτυον ἄλλοθεν ἄλλος·
Schol. QVB ad Od 10.441 ex
Q “Instead of the genitive here, “even though he was an in-law”.
QV For he married Odysseus’ sister Ktimene.
B “even though he was my brother-in-law by my sister Ktimenê.”
καὶ πηῷ] ἀντὶ τοῦ, καὶ πηοῦ περ ἐόντος. Q. συγγενεῖ. V.
Κτιμένην γὰρ γεγαμήκει τὴν ᾿Οδυσσέως ἀδελφήν. Q.V. γαμβρῷ
μοι ὄντι ἐπὶ τῇ ἀδελφῇ Κτιμένῃ. B.
“Pêos: A relative by marriage. In-law. Also, “in-lawness” [Pêosunê], relation-by-marriage. There is also Pêôn [genitive plural], for “of relatives-by-marriage. Homer has: “relatives and friends” [Il. 3.163]
Πηός: ὁ κατ’ ἐπιγαμίαν συγγενής. καὶ Πηοσύνη, ἡ συγγαμβρία.
καὶ Πηῶν, τῶν συγγενῶν. ῞Ομηρος· πηούς τε φίλους τε.
“…There is a difference between in-law and friend. People who have no connection to you by birth are friends. In-laws are related to you through marriage.”
διαφέρει δὲ πηὸς φίλου· φίλοι μὲν λέγονται οἱ μηδὲν τῷ γένει προσήκοντες· πηοὶ δὲ οἱ κατ’ ἐπιγαμίαν συγγενεῖς.
For a beautiful narrative re-imagining of the life of Ktimene, see Mary Ebbot’s “Seeking Odysseus’ Sister”