The best alternatives to KeywordSea are Ubersuggest, Frase, and Keyword Insights. If these 3 options don't work for you, we've listed a few more alternatives below.
Ubersuggest is a free SEO tool that specializes in generating new keyword ideas. Originally founded as a tool that scraped Google Suggest terms, Ubersuggest was recently acquired by entrepreneur Neil Patel, who has since expanded the feature set significantly.
Keyword insights utilise Geo-specific, live search engine result pages data to cluster keywords into similar groups while also working out their search intent. The output will save you hundreds of hours from your keyword research process.