Can. 1098 A person contracts invalidly who enters into a marriage deceived by malice, perpetrated to obtain consent, concerning some quality of the other partner which by its very nature can gravely disturb the partnership of conjugal life.
That’s basically fraud.
Apart from intentional deception, simple error, even without deception on the part of the other party, can be a ground too, so long as it involves a very specifically desired quality that determines the choice to marry or not:
Can. 1097 §1. Error concerning the person renders a marriage invalid.
§2. Error concerning a quality of the person does not render a marriage invalid even if it is the cause for the contract, unless this quality is directly and principally intended.
Simulation is a ground separate from deception and it occurs when people don’t consent to marriage, while they give apperance of so doing. Simulation of consent is related with exclusion - that is, exclusion of one of the three goods of marriage: offspring, faith, sacrament. This is regardless of deceipt of the other party. Consequently, one doesn’t marry validly while excluding children, exclusivity of marriage or indissolubility of it, even if the other party knows of the exclusion, or if both parties make the exclusion (e.g. a marriage of 10 years and no children is invalid no matter who knows about what and agrees to what).
Can. 1101 §1. The internal consent of the mind is presumed to conform to the words and signs used in celebrating the marriage.
§2. If, however, either or both of the parties by a positive act of the will exclude marriage itself, some essential element of marriage, or some essential property of marriage, the party contracts invalidly.
A case of someone pretending to want children while wanting none ever, would combine deception and simulation, but simulation would be the primary ground.
Someone being homosexual would be a problem on its own under canon 1095:
Can. 1095 The following are incapable of contracting marriage:
1/ those who lack the sufficient use of reason;
2/ those who suVer from a grave defect of discretion of judgment concerning the essential matrimonial rights and duties mutually to be handed over and accepted;
3/ those who are not able to assume the essential obligations of marriage for causes of a psychic nature.
Therefore in case of a person hiding a homosexual tendency, the primary problem would not be deception, but rather inability to have a functional marriage.