Yes Ravana killed his sister's husband.
As per this chapter of Valmiki Ramayana: Uttar Kanda:
And then going to the city named Asma ruled by the Kalakayas, Ravana() slew the Kalakayas endowed with terriffic striength ;and then with his sword cut of his brother.in law, the husband of Surpanakha, the mighty Vidyujjihva possessed of terriffic strength; as that Rakshasa in the encounter was licking (the limbs of Ravana s followers). Having vanquished him, he, in a moment, destroyed four hundred Daityas.
This is further clarified by Ravana to his sister in this chapter of Valmiki Ramayana: Uttar Kanada:
In the interval, Ravana s sister, a dreadful and grim visaged Rakshasi, suddenly fell down on to the ground. And having raised up his sister and consoled her Ravana said "Tell me speedily, O good sister, what you wish to say.
Thereat that Rakshasi, having blood red eyes, closed with tears, said "O king, by thee, powerful as thou art, I have forcibly been made a widow. Fourteen thousand Daityas, under the name of Kalakeyas, have been destroyed by thee, O king, in the battle and amongst them was my highly power ful husband dearer than my life. He has been slain by thee, O dear one, an enemy a brother only in name.
I have been killed by thee, O king, who art my brother. For thee, 0 king, I shall enjoy the word widow !My husband should have been saved by thee in the battle. But he was slain by thy ownself in the battle ;art thou not ashamed of this ?"Being thus addressed by his bewailing sister, the Dasagriva, consoling her in sweet words, said "Of no avail is thy lamentation, dear sister; thou needst not be afraid of any of thy relatives.
I shall please thee studiously by gifts, honors and favours. Being mad after war fare and desirous of acquiring victory,! was continually making a downpour of shafts, so I could not distinguish in the conflict between my own men and enemies, and thus unwittingly I did hurt thy husband. And thus, sister, thy husband was slain by me in the conflict; I shall now do whatever shall conduce to thy well being.
Do thou ever reside by the side of thy rich brother Khara and he shall be the lord of fourteen thousand Rakshasas. That highly powerful one shall give food and clothes to all those Rakshasas. He is thy cousin and that night ranger shall always carry out thy orders.