Sins

Tvastar Son of sukracharya  
https://en.wikipedia.org/wiki/Tvastar

Viśvarūpaor  - 1st son of Tvastar 
https://en.wikipedia.org/wiki/Trisiras

Sin of Indra

"Viswaroopa the son of Thwashta was recruited as the ‘guru’(priest) fore the gods in place of Bruhaspathi, when Bruhaspathi was hidden himself because of the insult made by the Indra. Viswaroopa was killed by Indra in a cheating war, then the Indra was attacked by the Brahma-hathya Dosha’. 

So now indra was suffering from the ‘brahma-hathya Dosha’. After some time he asks Bruhaspathi for solution, then Bruhaspathi said ‘if there is any body to share that, then you’ll be relieved and you should give some boons to the person’ 

The following shared the Brahma-hathya Dosha of indra in the following manner. 

1. Earth  (prithvy) shared the sin and releases the sin in the form of “fuller’s earth (choudu mritthika)” and got the boon that the earth will be filled or become closed even after the excavations. 
2. Trees (vriksha) shared the sin and releases the sin in the form of ‘gum’ and got the boon that they can grow even they cut. 
3. Sea(samudra)  shared the sin and released the sin in the form of ‘foam/froth’ and got the boon the at the sea cannot cross the sea shore (generally, not in some cases). 
4. Ladies (sthree) shared the sin and releases the sin in the form of ‘menstruation’ every month and got the boon that they can give birth to children from menstruation. "

http://haribhakt.com/sin-of-indra-and-curse-on-earth-sea-trees-and-women/

Vrtra - 2nd son of Tvastar 
https://en.wikipedia.org/wiki/Vritra

Sin of Indra

http://messengerofgods.blogspot.com/search/label/Chitraketu

Source
http://www.harekrsna.com/philosophy/associates/demons/indra/visvarupa.htm
http://www.prabhupada.de/Books/SB/06/13.html

Devi Version
http://www.kamakoti.org/kamakoti/details/skandapurana5.html