In the bottom of a double boiler, bring 1 inch water to simmer. Combine eggs, lemon juice, and sugar in top of double boiler and cook until thickened, about 10 to 12 minutes. Remove from heat and cool completely.
Using a standing mixer or electric hand mixer, whip heavy cream until stiff peaks form. Fold in cooled custard sauce until combined.
In a large bowl, add grapes, pineapple, oranges, cherries, marshmallows, and banana. Pour cream sauce over and stir to combine. Refrigerate at least 8 hours or up to 24 hours before serving.
