In the Collins Dictionary, the explanation for the word ingratiate is:
If someone <a href="https://www.collinsdictionary.com/dictionary/english/try" title="Definition of tries" class="ref type-def" style="overflow-wrap: break-word; margin: 0px; padding: 0px; border-width: 0px 0px 1px; border-top-style: initial; border-right-style: initial; border-bottom-style: dashed; border-left-style: initial; border-top-color: initial; border-right-color: initial; border-bottom-color: rgba(0, 0, 0, 0.6); border-left-color: initial; border-image: initial; font-family: "Open Sans", sans-serif; font-size: 20px; color: inherit; background-color: rgb(193, 230, 198);">tries</a> to ingratiate themselves with you, they do things to try and make you <a href="https://www.collinsdictionary.com/dictionary/english/like_1" title="Definition of like" class="ref type-def" style="overflow-wrap: break-word; margin: 0px; padding: 0px; border-width: 0px 0px 1px; border-top-style: initial; border-right-style: initial; border-bottom-style: dashed; border-left-style: initial; border-top-color: initial; border-right-color: initial; border-bottom-color: rgba(0, 0, 0, 0.6); border-left-color: initial; border-image: initial; font-family: "Open Sans", sans-serif; font-size: 20px; color: inherit; background-color: rgb(193, 230, 198);">like </a>them. (https://www.collinsdictionary.com/dictionary/english/ingratiate)
As I know 'someone' is singular, and this makes 'try' become 'tries'. but why is the latter 'themselves'?
Phil, that's a good point! I didn't consider yourself vs. yourselves. You're right it's actually the same thing. Convinced! :)